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Jing S, Yi X. Exome sequencing reveals PPEF2 variant associated with high myopia. Gene 2024; 897:148091. [PMID: 38110044 DOI: 10.1016/j.gene.2023.148091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 12/08/2023] [Accepted: 12/14/2023] [Indexed: 12/20/2023]
Abstract
High myopia (HM) is a serious blinding eye disease, and genetic factors play an important role in the development of HM. In this study, whole exome sequencing (WES) was used to identify a novel variant c.A875G of the PPEF2 for a large Uyghur family with nonsyndromic HM. The variant was verified to cosegregate with HM in the family using Sanger sequencing. Another novel variant c.1959C > G in PPEF2 was identified in one of 100 sporadic cases of HM by multiplex PCR targeted amplicon sequencing (MTA-seq). The Ppef2 was verified that mainly expressed in the retinal pigment epithelium (RPE), choroid and retina tissues. Immunofluorescence (IF) and immunohistochemistry (IHC) assays showed that the PPEF2 was strongly expressed in the inner segment layer formed by photoreceptor protrusions, as well as in the outer nuclear layer. Compared with the wild-type, the c.A875G resulted in reduced protein levels but had no effect on protein subcellular localization in cells. In addition, the c.A875G variant resulted in a decreased migratory and proliferative capacity but promoted apoptosis in cells. In summary, PPEF2 was identified as a novel HM-causing gene, and this variant in PPEF2 might cause HM by regulating the migration, proliferation and apoptosis of myopia-related cells.
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Affiliation(s)
- Sili Jing
- Shaanxi Eye Hospital, Xi'an People's Hospital (Xi'an Fourth Hospital), Affiliated People's Hospital of Northwest University, Xian, 710004, China; Ophthalmology, Xinjiang Medical University Affiliated First Hospital, Urumqi, Xinjiang, China
| | - Xianglong Yi
- Ophthalmology, Xinjiang Medical University Affiliated First Hospital, Urumqi, Xinjiang, China.
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Yang Y, Jiang X, Chen J, Liu L, Liu G, Sun K, Liu W, Zhu X, Guan Q. The m 6A reader YTHDC2 maintains visual function and retinal photoreceptor survival through modulating translation of PPEF2 and PDE6B. J Genet Genomics 2024; 51:208-221. [PMID: 38157933 DOI: 10.1016/j.jgg.2023.12.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 12/22/2023] [Accepted: 12/22/2023] [Indexed: 01/03/2024]
Abstract
Inherited retinal dystrophies (IRDs) are major causes of visual impairment and irreversible blindness worldwide, while the precise molecular and genetic mechanisms are still elusive. N6-methyladenosine (m6A) modification is the most prevalent internal modification in eukaryotic mRNA. YTH domain containing 2 (YTHDC2), an m6A reader protein, has recently been identified as a key player in germline development and human cancer. However, its contribution to retinal function remains unknown. Here, we explore the role of YTHDC2 in the visual function of retinal rod photoreceptors by generating rod-specific Ythdc2 knockout mice. Results show that Ythdc2 deficiency in rods causes diminished scotopic ERG responses and progressive retinal degeneration. Multi-omics analysis further identifies Ppef2 and Pde6b as the potential targets of YTHDC2 in the retina. Specifically, via its YTH domain, YTHDC2 recognizes and binds m6A-modified Ppef2 mRNA at the coding sequence and Pde6b mRNA at the 5'-UTR, resulting in enhanced translation efficiency without affecting mRNA levels. Compromised translation efficiency of Ppef2 and Pde6b after YTHDC2 depletion ultimately leads to decreased protein levels in the retina, impaired retinal function, and progressive rod death. Collectively, our finding highlights the importance of YTHDC2 in visual function and photoreceptor survival, which provides an unreported elucidation of IRD pathogenesis via epitranscriptomics.
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Affiliation(s)
- Yeming Yang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Xiaoyan Jiang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Junyao Chen
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Lu Liu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Guo Liu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Kuanxiang Sun
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Wenjing Liu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Xianjun Zhu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China; Department of Geriatrics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China; Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan 610072, China; Qinghai Key Laboratory of Qinghai Tibet Plateau Biological Resources, Chinese Academy of Sciences and Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, Qinghai 810008, China; Henan Eye Institute, Henan Eye Hospital, People's Hospital of Zhengzhou University, Henan Provincial People's Hospital, Zhengzhou, Henan 450003, China.
| | - Qiuyue Guan
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China; Department of Geriatrics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China.
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Smylla TK, Wagner K, Huber A. The Role of Reversible Phosphorylation of Drosophila Rhodopsin. Int J Mol Sci 2022; 23:ijms232314674. [PMID: 36499010 PMCID: PMC9740569 DOI: 10.3390/ijms232314674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/18/2022] [Accepted: 11/21/2022] [Indexed: 11/27/2022] Open
Abstract
Vertebrate and fly rhodopsins are prototypical GPCRs that have served for a long time as model systems for understanding GPCR signaling. Although all rhodopsins seem to become phosphorylated at their C-terminal region following activation by light, the role of this phosphorylation is not uniform. Two major functions of rhodopsin phosphorylation have been described: (1) inactivation of the activated rhodopsin either directly or by facilitating binding of arrestins in order to shut down the visual signaling cascade and thus eventually enabling a high-temporal resolution of the visual system. (2) Facilitating endocytosis of activated receptors via arrestin binding that in turn recruits clathrin to the membrane for clathrin-mediated endocytosis. In vertebrate rhodopsins the shutdown of the signaling cascade may be the main function of rhodopsin phosphorylation, as phosphorylation alone already quenches transducin activation and, in addition, strongly enhances arrestin binding. In the Drosophila visual system rhodopsin phosphorylation is not needed for receptor inactivation. Its role here may rather lie in the recruitment of arrestin 1 and subsequent endocytosis of the activated receptor. In this review, we summarize investigations of fly rhodopsin phosphorylation spanning four decades and contextualize them with regard to the most recent insights from vertebrate phosphorylation barcode theory.
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Subramanian R, Sahoo D. Boolean implication analysis of single-cell data predicts retinal cell type markers. BMC Bioinformatics 2022; 23:378. [PMID: 36114457 PMCID: PMC9482279 DOI: 10.1186/s12859-022-04915-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 08/25/2022] [Indexed: 11/15/2022] Open
Abstract
Background The retina is a complex tissue containing multiple cell types that are essential for vision. Understanding the gene expression patterns of various retinal cell types has potential applications in regenerative medicine. Retinal organoids (optic vesicles) derived from pluripotent stem cells have begun to yield insights into the transcriptomics of developing retinal cell types in humans through single cell RNA-sequencing studies. Previous methods of gene reporting have relied upon techniques in vivo using microarray data, or correlational and dimension reduction methods for analyzing single cell RNA-sequencing data computationally. We aimed to develop a state-of-the-art Boolean method that filtered out noise, could be applied to a wide variety of datasets and lent insight into gene expression over differentiation. Results Here, we present a bioinformatic approach using Boolean implication to discover genes which are retinal cell type-specific or involved in retinal cell fate. We apply this approach to previously published retina and retinal organoid datasets and improve upon previously published correlational methods. Our method improves the prediction accuracy of marker genes of retinal cell types and discovers several new high confidence cone and rod-specific genes. Conclusions The results of this study demonstrate the benefits of a Boolean approach that considers asymmetric relationships. We have shown a statistically significant improvement from correlational, symmetric methods in the prediction accuracy of retinal cell-type specific genes. Furthermore, our method contains no cell or tissue-specific tuning and hence could impact other areas of gene expression analyses in cancer and other human diseases. Supplementary Information The online version contains supplementary material available at 10.1186/s12859-022-04915-4.
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Transcriptome-Guided Identification of Drugs for Repurposing to Treat Age-Related Hearing Loss. Biomolecules 2022; 12:biom12040498. [PMID: 35454087 PMCID: PMC9028743 DOI: 10.3390/biom12040498] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 03/13/2022] [Accepted: 03/22/2022] [Indexed: 02/04/2023] Open
Abstract
Age-related hearing loss (ARHL) or presbycusis is a prevalent condition associated with social isolation, cognitive impairment, and dementia. Age-related changes in the cochlea, the auditory portion of the inner ear, are the primary cause of ARHL. Unfortunately, there are currently no pharmaceutical approaches to treat ARHL. To examine the biological processes underlying age-related changes in the cochlea and identify candidate drugs for rapid repurposing to treat ARHL, we utilized bulk RNA sequencing to obtain transcriptomes from the functional substructures of the cochlea—the sensorineural structures, including the organ of Corti and spiral ganglion neurons (OC/SGN) and the stria vascularis and spiral ligament (SV/SL)—in young (6-week-old) and old (2-year-old) C57BL/6 mice. Transcriptomic analyses revealed both overlapping and unique patterns of gene expression and gene enrichment between substructures and with ageing. Based on these age-related transcriptional changes, we queried the protein products of genes differentially expressed with ageing in DrugBank and identified 27 FDA/EMA-approved drugs that are suitable to be repurposed to treat ARHL. These drugs target the protein products of genes that are differentially expressed with ageing uniquely in either the OC/SGN or SV/SL and that interrelate diverse biological processes. Further transcriptomic analyses revealed that most genes differentially expressed with ageing in both substructures encode protein products that are promising drug target candidates but are, nevertheless, not yet linked to approved drugs. Thus, with this study, we apply a novel approach to characterize the druggable genetic landscape for ARHL and propose a list of drugs to test in pre-clinical studies as potential treatment options for ARHL.
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Lavoie-Ouellet C, Clark MÈ, Ruiz J, Saindon AA, Leclerc P. The protein phosphatase with EF-hand domain 1 is a calmodulin-binding protein that interacts with proteins involved in sperm capacitation, binding to the zona pellucida, and motility. Mol Reprod Dev 2021; 88:302-317. [PMID: 33783058 DOI: 10.1002/mrd.23467] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 11/12/2022]
Abstract
Spermatozoa are highly specialized cells whose fertilizing and motility functions highly depend on intracellular Ca2+ -mediated events and protein posttranslational modifications like phosphorylation. Our group previously identified PPEF1, the Ser/Thr phosphatase with EF-hand domain 1, among calmodulin-affinity pulled down sperm proteins. As the mammalian ortholog of the Drosophila phosphatase rdgC that dephosphorylates rhodopsin, PPEF1 has been studied mostly in the retina. The presence and importance of this Ca2+ /calmodulin-binding protein phosphatase has not been studied in sperm or testicular functions despite its high expression level. In this study, we show that PPEF1 is present in testicular germ cells, and in mouse, human and bull spermatozoa where it is localized predominantly in the neck and acrosome areas. Different transcript variants encoding four predicted isoforms were detected by reverse transcription polymerase chain reaction in bull testis, spermatocytes and spermatids. Phosphatase activity of immunoprecipitated sperm PPEF1 was detected using the substrate pNPP and analysis of the coimmunoprecipitated proteins reveal an enrichment in the biological processes of sperm capacitation, binding to the zona pellucida and motility. Although this is the first demonstration of the presence of PPEF1 in sperm and testicular germ cells, its involvement in sperm fertilizing ability and motility, and the mechanisms regulating its activity remain to be further investigated.
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Affiliation(s)
- Camille Lavoie-Ouellet
- Département d'Obstétrique, gynécologie et reproduction, Centre de recherche en reproduction, développement et santé intergénérationnelle, Université Laval, Axe reproduction, santé de la mère et de l'enfant, Centre de recherche du CHU de Québec-Université Laval, Quebec City, Québec, Canada
| | - Marie-Ève Clark
- Département d'Obstétrique, gynécologie et reproduction, Centre de recherche en reproduction, développement et santé intergénérationnelle, Université Laval, Axe reproduction, santé de la mère et de l'enfant, Centre de recherche du CHU de Québec-Université Laval, Quebec City, Québec, Canada
| | - Juliana Ruiz
- Département d'Obstétrique, gynécologie et reproduction, Centre de recherche en reproduction, développement et santé intergénérationnelle, Université Laval, Axe reproduction, santé de la mère et de l'enfant, Centre de recherche du CHU de Québec-Université Laval, Quebec City, Québec, Canada
| | - Andrée-Anne Saindon
- Département d'Obstétrique, gynécologie et reproduction, Centre de recherche en reproduction, développement et santé intergénérationnelle, Université Laval, Axe reproduction, santé de la mère et de l'enfant, Centre de recherche du CHU de Québec-Université Laval, Quebec City, Québec, Canada
| | - Pierre Leclerc
- Département d'Obstétrique, gynécologie et reproduction, Centre de recherche en reproduction, développement et santé intergénérationnelle, Université Laval, Axe reproduction, santé de la mère et de l'enfant, Centre de recherche du CHU de Québec-Université Laval, Quebec City, Québec, Canada
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Novel eye genes systematically discovered through an integrated analysis of mouse transcriptomes and phenome. Comput Struct Biotechnol J 2019; 18:73-82. [PMID: 31934309 PMCID: PMC6951830 DOI: 10.1016/j.csbj.2019.12.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 12/04/2019] [Accepted: 12/14/2019] [Indexed: 01/23/2023] Open
Abstract
In the last few decades, reverse genetic and high throughput approaches have been frequently applied to the mouse (Mus musculus) to understand how genes function in tissues/organs and during development in a mammalian system. Despite these efforts, the associated phenotypes for the majority of mouse genes remained to be fully characterized. Here, we performed an integrated transcriptome-phenome analysis by identifying coexpressed gene modules based on tissue transcriptomes profiled with each of various platforms and functionally interpreting these modules using the mouse phenotypic data. Consequently, >15,000 mouse genes were linked with at least one of the 47 tissue functions that were examined. Specifically, our approach predicted >50 genes previously unknown to be involved in mice (Mus musculus) visual functions. Fifteen genes were selected for further analysis based on their potential biomedical relevance and compatibility with further experimental validation. Gene-specific morpholinos were introduced into zebrafish (Danio rerio) to target their corresponding orthologs. Quantitative assessments of phenotypes of developing eyes confirmed predicted eye-related functions of 13 out of the 15 genes examined. These novel eye genes include: Adal, Ankrd33, Car14, Ccdc126, Dhx32, Dkk3, Fam169a, Grifin, Kcnj14, Lrit2, Ppef2, Ppm1n, and Wdr17. The results highlighted the potential for this phenome-based approach to assist the experimental design of mutating and phenotyping mouse genes that aims to fully reveal the functional landscape of mammalian genomes.
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Brautigan DL, Shenolikar S. Protein Serine/Threonine Phosphatases: Keys to Unlocking Regulators and Substrates. Annu Rev Biochem 2019; 87:921-964. [PMID: 29925267 DOI: 10.1146/annurev-biochem-062917-012332] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protein serine/threonine phosphatases (PPPs) are ancient enzymes, with distinct types conserved across eukaryotic evolution. PPPs are segregated into types primarily on the basis of the unique interactions of PPP catalytic subunits with regulatory proteins. The resulting holoenzymes dock substrates distal to the active site to enhance specificity. This review focuses on the subunit and substrate interactions for PPP that depend on short linear motifs. Insights about these motifs from structures of holoenzymes open new opportunities for computational biology approaches to elucidate PPP networks. There is an expanding knowledge base of posttranslational modifications of PPP catalytic and regulatory subunits, as well as of their substrates, including phosphorylation, acetylation, and ubiquitination. Cross talk between these posttranslational modifications creates PPP-based signaling. Knowledge of PPP complexes, signaling clusters, as well as how PPPs communicate with each other in response to cellular signals should unlock the doors to PPP networks and signaling "clouds" that orchestrate and coordinate different aspects of cell physiology.
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Affiliation(s)
- David L Brautigan
- Center for Cell Signaling and Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA;
| | - Shirish Shenolikar
- Signature Research Programs in Cardiovascular and Metabolic Disorders and Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore 169857
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Zwick M, Ulas T, Cho YL, Ried C, Grosse L, Simon C, Bernhard C, Busch DH, Schultze JL, Buchholz VR, Stutte S, Brocker T. Expression of the Phosphatase Ppef2 Controls Survival and Function of CD8 + Dendritic Cells. Front Immunol 2019; 10:222. [PMID: 30809231 PMCID: PMC6379467 DOI: 10.3389/fimmu.2019.00222] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 01/25/2019] [Indexed: 11/25/2022] Open
Abstract
Apoptotic cell death of Dendritic cells (DCs) is critical for immune homeostasis. Although intrinsic mechanisms controlling DC death have not been fully characterized up to now, experimentally enforced inhibition of DC-death causes various autoimmune diseases in model systems. We have generated mice deficient for Protein Phosphatase with EF-Hands 2 (Ppef2), which is selectively expressed in CD8+ DCs, but not in other related DC subtypes such as tissue CD103+ DCs. Ppef2 is down-regulated rapidly upon maturation of DCs by toll-like receptor stimuli, but not upon triggering of CD40. Ppef2-deficient CD8+ DCs accumulate the pro-apoptotic Bcl-2-like protein 11 (Bim) and show increased apoptosis and reduced competitve repopulation capacities. Furthermore, Ppef2−/− CD8+ DCs have strongly diminished antigen presentation capacities in vivo, as CD8+ T cells primed by Ppef2−/− CD8+ DCs undergo reduced expansion. In conclusion, our data suggests that Ppef2 is crucial to support survival of immature CD8+ DCs, while Ppef2 down-regulation during DC-maturation limits T cell responses.
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Affiliation(s)
- Markus Zwick
- Faculty of Medicine, Biomedical Center (BMC), Institute for Immunology, LMU Munich, Planegg-Martinsried, Germany
| | - Thomas Ulas
- Life and Medical Sciences Institute, Bonn, Germany
| | - Yi-Li Cho
- Institute for Medical Microbiology, Immunology and Hygiene, Technische Universität München, Munich, Germany
| | - Christine Ried
- Faculty of Medicine, Biomedical Center (BMC), Institute for Immunology, LMU Munich, Planegg-Martinsried, Germany
| | - Leonie Grosse
- Faculty of Medicine, Biomedical Center (BMC), Institute for Immunology, LMU Munich, Planegg-Martinsried, Germany
| | - Charlotte Simon
- Faculty of Medicine, Biomedical Center (BMC), Institute for Immunology, LMU Munich, Planegg-Martinsried, Germany
| | - Caroline Bernhard
- Faculty of Medicine, Biomedical Center (BMC), Institute for Immunology, LMU Munich, Planegg-Martinsried, Germany
| | - Dirk H Busch
- Institute for Medical Microbiology, Immunology and Hygiene, Technische Universität München, Munich, Germany
| | - Joachim L Schultze
- Life and Medical Sciences Institute, Bonn, Germany.,PRECISE-Platform for Single Cell Genomics and Epigenomics at the German Center for Neurodegenerative Diseases (DZNE) and the University of Bonn, Bonn, Germany
| | - Veit R Buchholz
- Institute for Medical Microbiology, Immunology and Hygiene, Technische Universität München, Munich, Germany
| | - Susanne Stutte
- Faculty of Medicine, Biomedical Center (BMC), Institute for Immunology, LMU Munich, Planegg-Martinsried, Germany
| | - Thomas Brocker
- Faculty of Medicine, Biomedical Center (BMC), Institute for Immunology, LMU Munich, Planegg-Martinsried, Germany
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Strauch L, Pfannstiel J, Huber A, Voolstra O. Solubility and subcellular localization of the three Drosophila RDGC phosphatase variants are determined by acylation. FEBS Lett 2018; 592:2403-2413. [PMID: 29920663 DOI: 10.1002/1873-3468.13163] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 06/06/2018] [Accepted: 06/11/2018] [Indexed: 01/26/2023]
Abstract
Protein phosphorylation is an abundant molecular switch that regulates a multitude of cellular processes. In contrast to other subfamilies of phosphoprotein phosphatases, the PPEF subfamily is only poorly investigated. Drosophila retinal degeneration C (RDGC) constitutes the founding member of the PPEF subfamily. RDGC dephosphorylates the visual pigment rhodopsin and the ion channel TRP.However, rdgC null mutant flies exhibit rhodopsin and TRP hyperphosphorylation, altered photoreceptor physiology, and retinal degeneration. Here, we report the identification of a third RDGC protein variant and show that the three RDGC isoforms harbor different N-termini that determine solubility and subcellular targeting due to fatty acylation. Taken together, solubility and subcellular targeting of RDGC splice variants are determined by their N-termini.
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Affiliation(s)
- Lisa Strauch
- Department of Biosensorics, Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Jens Pfannstiel
- Core Facility, Mass Spectrometry Unit, University of Hohenheim, Stuttgart, Germany
| | - Armin Huber
- Department of Biosensorics, Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Olaf Voolstra
- Department of Biosensorics, Institute of Physiology, University of Hohenheim, Stuttgart, Germany
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Dephosphorylation by protein phosphatase 2A regulates visual pigment regeneration and the dark adaptation of mammalian photoreceptors. Proc Natl Acad Sci U S A 2017; 114:E9675-E9684. [PMID: 29078372 DOI: 10.1073/pnas.1712405114] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Resetting of G-protein-coupled receptors (GPCRs) from their active state back to their biologically inert ground state is an integral part of GPCR signaling. This "on-off" GPCR cycle is regulated by reversible phosphorylation. Retinal rod and cone photoreceptors arguably represent the best-understood example of such GPCR signaling. Their visual pigments (opsins) are activated by light, transduce the signal, and are then inactivated by a GPCR kinase and arrestin. Although pigment inactivation by phosphorylation is well understood, the enzyme(s) responsible for pigment dephosphorylation and the functional significance of this reaction remain unknown. Here, we show that protein phosphatase 2A (PP2A) acts as opsin phosphatase in both rods and cones. Elimination of PP2A substantially slows pigment dephosphorylation, visual chromophore recycling, and ultimately photoreceptor dark adaptation. These findings demonstrate that visual pigment dephosphorylation regulates the dark adaptation of photoreceptors and provide insights into the role of this reaction in GPCR signaling.
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12
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Effect of Rhodopsin Phosphorylation on Dark Adaptation in Mouse Rods. J Neurosci 2017; 36:6973-87. [PMID: 27358455 DOI: 10.1523/jneurosci.3544-15.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 05/17/2016] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED Rhodopsin is a prototypical G-protein-coupled receptor (GPCR) that is activated when its 11-cis-retinal moiety is photoisomerized to all-trans retinal. This step initiates a cascade of reactions by which rods signal changes in light intensity. Like other GPCRs, rhodopsin is deactivated through receptor phosphorylation and arrestin binding. Full recovery of receptor sensitivity is then achieved when rhodopsin is regenerated through a series of steps that return the receptor to its ground state. Here, we show that dephosphorylation of the opsin moiety of rhodopsin is an extremely slow but requisite step in the restoration of the visual pigment to its ground state. We make use of a novel observation: isolated mouse retinae kept in standard media for routine physiologic recordings display blunted dephosphorylation of rhodopsin. Isoelectric focusing followed by Western blot analysis of bleached isolated retinae showed little dephosphorylation of rhodopsin for up to 4 h in darkness, even under conditions when rhodopsin was completely regenerated. Microspectrophotometeric determinations of rhodopsin spectra show that regenerated phospho-rhodopsin has the same molecular photosensitivity as unphosphorylated rhodopsin and that flash responses measured by trans-retinal electroretinogram or single-cell suction electrode recording displayed dark-adapted kinetics. Single quantal responses displayed normal dark-adapted kinetics, but rods were only half as sensitive as those containing exclusively unphosphorylated rhodopsin. We propose a model in which light-exposed retinae contain a mixed population of phosphorylated and unphosphorylated rhodopsin. Moreover, complete dark adaptation can only occur when all rhodopsin has been dephosphorylated, a process that requires >3 h in complete darkness. SIGNIFICANCE STATEMENT G-protein-coupled receptors (GPCRs) constitute the largest superfamily of proteins that compose ∼4% of the mammalian genome whose members share a common membrane topology. Signaling by GPCRs regulate a wide variety of physiological processes, including taste, smell, hearing, vision, and cardiovascular, endocrine, and reproductive homeostasis. An important feature of GPCR signaling is its timely termination. This normally occurs when, after their activation, GPCRs are rapidly phosphorylated by specific receptor kinases and subsequently bound by cognate arrestins. Recovery of receptor sensitivity to the ground state then requires dephosphorylation of the receptor and unbinding of arrestin, processes that are poorly understood. Here we investigate in mouse rod photoreceptors the relationship between rhodopsin dephosphorylation and recovery of visual sensitivity.
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13
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The Phosphorylation State of the Drosophila TRP Channel Modulates the Frequency Response to Oscillating Light In Vivo. J Neurosci 2017; 37:4213-4224. [PMID: 28314815 DOI: 10.1523/jneurosci.3670-16.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 02/13/2017] [Accepted: 02/28/2017] [Indexed: 11/21/2022] Open
Abstract
Drosophila photoreceptors respond to oscillating light of high frequency (∼100 Hz), while the detected maximal frequency is modulated by the light rearing conditions, thus enabling high sensitivity to light and high temporal resolution. However, the molecular basis for this adaptive process is unclear. Here, we report that dephosphorylation of the light-activated transient receptor potential (TRP) ion channel at S936 is a fast, graded, light-dependent, and Ca2+-dependent process that is partially modulated by the rhodopsin phosphatase retinal degeneration C (RDGC). Electroretinogram measurements of the frequency response to oscillating lights in vivo revealed that dark-reared flies expressing wild-type TRP exhibited a detection limit of oscillating light at relatively low frequencies, which was shifted to higher frequencies upon light adaptation. Strikingly, preventing phosphorylation of the S936-TRP site by alanine substitution in transgenic Drosophila (trpS936A ) abolished the difference in frequency response between dark-adapted and light-adapted flies, resulting in high-frequency response also in dark-adapted flies. In contrast, inserting a phosphomimetic mutation by substituting the S936-TRP site to aspartic acid (trpS936D ) set the frequency response of light-adapted flies to low frequencies typical of dark-adapted flies. Light-adapted rdgC mutant flies showed relatively high S936-TRP phosphorylation levels and light-dark phosphorylation dynamics. These findings suggest that RDGC is one but not the only phosphatase involved in pS936-TRP dephosphorylation. Together, this study indicates that TRP channel dephosphorylation is a regulatory process that affects the detection limit of oscillating light according to the light rearing condition, thus adjusting dynamic processing of visual information under varying light conditions.SIGNIFICANCE STATEMENTDrosophila photoreceptors exhibit high temporal resolution as manifested in frequency response to oscillating light of high frequency (≤∼100 Hz). Light rearing conditions modulate the maximal frequency detected by photoreceptors, thus enabling them to maintain high sensitivity to light and high temporal resolution. However, the precise mechanisms for this process are not fully understood. Here, we show by combination of biochemistry and in vivo electrophysiology that transient receptor potential (TRP) channel dephosphorylation at a specific site is a fast, light-activated and Ca2+-dependent regulatory process. TRP dephosphorylation affects the detection limit of oscillating light according to the adaptation state of the photoreceptor cells by shifting the detection limit to higher frequencies upon light adaptation. This novel mechanism thus adjusts dynamic processing of visual information under varying light conditions.
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Bojjireddy N, Guzman-Hernandez ML, Reinhard NR, Jovic M, Balla T. EFR3s are palmitoylated plasma membrane proteins that control responsiveness to G-protein-coupled receptors. J Cell Sci 2014; 128:118-28. [PMID: 25380825 DOI: 10.1242/jcs.157495] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The yeast Efr3p protein is a main regulator of the Stt4p phosphatidylinositol 4-kinase at contact sites between the endoplasmic reticulum and the plasma membrane. A mutation in its fly homologue Rbo, leads to diminished light responses in the eye attributed to progressively impaired PLC signaling. Here, we find that Efr3s plays a role in maintaining responsiveness to the type-I angiotensin II (AngII) receptors. siRNA-mediated depletion of EFR3A and EFR3B impaired the sustained phase of cytosolic Ca(2+) response to high concentration of AngII in HEK293 cells that express wild type but not truncated AGTR1 (AT1a receptor), missing the phosphorylation sites. Efr3 depletion had minimal effect on the recovery of plasma membrane phosphoinositides during stimulation, and AT1 receptors still underwent ligand-induced internalization. A higher level of basal receptor phosphorylation and a larger response was observed after stimulation. Moreover, Gq activation more rapidly desensitized after AngII stimulation in Efr3 downregulated cells. A similar but less pronounced effect of EFR3 depletion was observed on the desensitization of the cAMP response after stimulation with isoproterenol. These data suggest that mammalian Efr3s contribute to the control of the phosphorylation state and, hence, desensitization of AT1a receptors, and could affect responsiveness of G-protein-coupled receptors in higher eukaryotes.
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Affiliation(s)
- Naveen Bojjireddy
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA
| | - Maria Luisa Guzman-Hernandez
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA
| | - Nathalie Renée Reinhard
- Swammerdam Institute for Life Sciences, University of Amsterdam, 1012 WX Amsterdam, The Netherlands
| | - Marko Jovic
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA
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Saitsu H, Osaka H, Nishiyama K, Tsurusaki Y, Doi H, Miyake N, Matsumoto N. A girl with early-onset epileptic encephalopathy associated with microdeletion involving CDKL5. Brain Dev 2012; 34:364-7. [PMID: 21802232 DOI: 10.1016/j.braindev.2011.07.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 06/21/2011] [Accepted: 07/05/2011] [Indexed: 01/08/2023]
Abstract
Recent studies have shown that aberrations of CDKL5 in female patients cause early-onset intractable seizures, severe developmental delay or regression, and Rett syndrome-like features. We report on a Japanese girl with early-onset epileptic encephalopathy, hypotonia, developmental regression, and Rett syndrome-like features. The patient showed generalized tonic seizures, and later, massive myoclonus induced by phone and light stimuli. Brain magnetic resonance imaging showed no structural brain anomalies but cerebral atrophy. Electroencephalogram showed frontal dominant diffuse poly spikes and waves. Through copy number analysis by genomic microarray, we found a microdeletion at Xp22.13. A de novo 137-kb deletion, involving exons 5-21 of CDKL5, RS1, and part of PPEF1 gene, was confirmed by quantitative PCR and breakpoint specific PCR analyses. Our report suggests that the clinical features associated with CDKL5 deletions could be implicated in Japanese patients, and that genetic testing of CDKL5, including both sequencing and deletion analyses, should be considered in girls with early-onset epileptic encephalopathy and RTT-like features.
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Affiliation(s)
- Hirotomo Saitsu
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
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Kutuzov MA, Bennett N, Andreeva AV. Protein phosphatase with EF-hand domains 2 (PPEF2) is a potent negative regulator of apoptosis signal regulating kinase-1 (ASK1). Int J Biochem Cell Biol 2010; 42:1816-22. [PMID: 20674765 DOI: 10.1016/j.biocel.2010.07.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 07/09/2010] [Accepted: 07/21/2010] [Indexed: 11/28/2022]
Abstract
The function of protein phosphatases with EF-hand domains (PPEF) in mammals is not known. Large-scale expression profiling experiments suggest that PPEF expression may correlate with stress protective responses, cell survival, growth, proliferation, or neoplastic transformation. Apoptosis signal regulating kinase-1 (ASK1) is a MAP kinase kinase kinase implicated in cancer, cardiovascular and neurodegenerative diseases. ASK1 is activated by oxidative stress and induces pro-apoptotic or inflammatory signalling, largely via sustained activation of MAP kinases p38 and/or JNK. We identify human PPEF2 as a novel interacting partner and a negative regulator of ASK1. In COS-7 or HEK 293A cells treated with H(2)O(2), expression of PPEF2 abrogated sustained activation of p38 and one of the JNK p46 isoforms, and prevented ASK1-dependent caspase-3 cleavage and activation. PPEF2 efficiently suppressed H(2)O(2)-induced activation of ASK1. Overexpessed as well as endogenous ASK1 co-immunoprecipitated with PPEF2. PPEF2 was considerably more potent both as a suppressor of ASK1 activation and as its interacting partner as compared to protein phosphatase 5 (PP5), a well-known negative regulator of ASK1. PPEF2 was found to form complexes with endogenous Hsp70 and to a lesser extent Hsp90, which are also known interacting partners of PP5. These data identify, for the first time, a possible downstream signalling partner of a mammalian PPEF phosphatase, and suggest that, despite structural divergence, PPEF and PP5 phosphatases may share common interacting partners and functions.
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Affiliation(s)
- Mikhail A Kutuzov
- Department of Pharmacology (MC 868), University of Illinois at Chicago, Chicago, IL 60612, USA.
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Andreeva AV, Kutuzov MA. PPEF/PP7 protein Ser/Thr phosphatases. Cell Mol Life Sci 2009; 66:3103-10. [PMID: 19662497 PMCID: PMC11115641 DOI: 10.1007/s00018-009-0110-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2009] [Accepted: 07/15/2009] [Indexed: 12/14/2022]
Abstract
PPEF/PP7 represents one of the five subfamilies of the PPP protein Ser/Thr phosphatases. Studies published in recent years point to a role of plant PP7 at a crossroad of different pathways of light and stress signalling. In animals, PPEFs are highly expressed in sensory neurons, and Drosophila PPEF phosphatase, rdgC, is essential for dephosphorylation of rhodopsin. Expression profiling suggests that mammalian PPEF may play a role in stress-protective responses, cell survival, growth, proliferation, and oncogenesis. Despite structural similarities of the catalytic domains and the fact that some of these phosphatases are involved in light perception both in animals and in plants, the plant and non-plant representatives of this group have distinct domain architecture and appear not to be orthologues.
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Affiliation(s)
- Alexandra V. Andreeva
- Department of Pharmacology (M/C 868), College of Medicine, University of Illinois, 909 S. Wolcott Ave., Chicago, IL 60612 USA
| | - Mikhail A. Kutuzov
- Department of Pharmacology (M/C 868), College of Medicine, University of Illinois, 909 S. Wolcott Ave., Chicago, IL 60612 USA
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Mills E, Price HP, Johner A, Emerson JE, Smith DF. Kinetoplastid PPEF phosphatases: dual acylated proteins expressed in the endomembrane system of Leishmania. Mol Biochem Parasitol 2006; 152:22-34. [PMID: 17169445 PMCID: PMC1885993 DOI: 10.1016/j.molbiopara.2006.11.008] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Revised: 11/02/2006] [Accepted: 11/14/2006] [Indexed: 12/02/2022]
Abstract
Bioinformatic analyses have been used to identify potential downstream targets of the essential enzyme N-myristoyl transferase in the TriTryp species, Leishmania major, Trypanosoma brucei and Trypanosoma cruzi. These database searches predict ∼60 putative N-myristoylated proteins with high confidence, including both previously characterised and novel molecules. One of the latter is an N-myristoylated protein phosphatase which has high sequence similarity to the Protein Phosphatase with EF-Hand (PPEF) proteins identified in sensory cells of higher eukaryotes. In L. major and T. brucei, the PPEF-like phosphatases are encoded by single-copy genes and are constitutively expressed in all parasite life cycle stages. The N-terminus of LmPPEF is a substrate for N-myristoyl transferase and is also palmitoylated in vivo. The wild type protein has been localised to the endocytic system by immunofluorescence. The catalytic and fused C-terminal domains of the kinetoplastid and other eukaryotic PPEFs share high sequence similarity, but unlike their higher eukaryotic relatives, the C-terminal parasite EF-hand domains are degenerate and do not bind calcium.
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Affiliation(s)
- Elena Mills
- Wellcome Trust Laboratories for Molecular Parasitology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, UK
| | - Helen P. Price
- Wellcome Trust Laboratories for Molecular Parasitology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, UK
- Immunology and Infection Unit, Department of Biology, University of York, Heslington, York YO10 5YW, UK
| | - Andrea Johner
- Immunology and Infection Unit, Department of Biology, University of York, Heslington, York YO10 5YW, UK
| | - Jenny E. Emerson
- Wellcome Trust Laboratories for Molecular Parasitology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, UK
| | - Deborah F. Smith
- Wellcome Trust Laboratories for Molecular Parasitology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, UK
- Immunology and Infection Unit, Department of Biology, University of York, Heslington, York YO10 5YW, UK
- Corresponding author at: Immunology and Infection Unit, Department of Biology, University of York, Heslington, York YO10 5YW, UK. Tel.: +44 1904 328843; fax: +44 1904 328844.
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Byrum CA, Walton KD, Robertson AJ, Carbonneau S, Thomason RT, Coffman JA, McClay DR. Protein tyrosine and serine-threonine phosphatases in the sea urchin, Strongylocentrotus purpuratus: identification and potential functions. Dev Biol 2006; 300:194-218. [PMID: 17087928 PMCID: PMC3045532 DOI: 10.1016/j.ydbio.2006.08.050] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 08/18/2006] [Accepted: 08/19/2006] [Indexed: 10/24/2022]
Abstract
Protein phosphatases, in coordination with protein kinases, play crucial roles in regulation of signaling pathways. To identify protein tyrosine phosphatases (PTPs) and serine-threonine (ser-thr) phosphatases in the Strongylocentrotus purpuratus genome, 179 annotated sequences were studied (122 PTPs, 57 ser-thr phosphatases). Sequence analysis identified 91 phosphatases (33 conventional PTPs, 31 dual specificity phosphatases, 1 Class III Cysteine-based PTP, 1 Asp-based PTP, and 25 ser-thr phosphatases). Using catalytic sites, levels of conservation and constraint in amino acid sequence were examined. Nine of 25 receptor PTPs (RPTPs) corresponded to human, nematode, or fly homologues. Domain structure revealed that sea urchin-specific RPTPs including two, PTPRLec and PTPRscav, may act in immune defense. Embryonic transcription of each phosphatase was recorded from a high-density oligonucleotide tiling microarray experiment. Most RPTPs are expressed at very low levels, whereas nonreceptor PTPs (NRPTPs) are generally expressed at moderate levels. High expression was detected in MAP kinase phosphatases (MKPs) and numerous ser-thr phosphatases. For several expressed NRPTPs, MKPs, and ser-thr phosphatases, morpholino antisense-mediated knockdowns were performed and phenotypes obtained. Finally, to assess roles of annotated phosphatases in endomesoderm formation, a literature review of phosphatase functions in model organisms was superimposed on sea urchin developmental pathways to predict areas of functional activity.
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Affiliation(s)
- C A Byrum
- Developmental, Cell, and Molecular Biology Group, Box 91000, Duke University, Durham, NC 27708, USA.
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Lee SJ, Xu H, Montell C. Rhodopsin kinase activity modulates the amplitude of the visual response in Drosophila. Proc Natl Acad Sci U S A 2004; 101:11874-9. [PMID: 15289614 PMCID: PMC511067 DOI: 10.1073/pnas.0402205101] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A feature shared between Drosophila rhodopsin and nearly all other G protein-coupled receptors is agonist-dependent protein phosphorylation. Despite extensive analyses of Drosophila phototransduction, the identity and function of the rhodopsin kinase (RK) have been elusive. Here, we provide evidence that G protein-coupled receptor kinase 1 (GPRK1), which is most similar to the beta-adrenergic receptor kinases, G protein-coupled receptor kinase 2 (GRK2) and GRK3, is the fly RK. We show that GPRK1 is enriched in photoreceptor cells, associates with the major Drosophila rhodopsin, Rh1, and phosphorylates the receptor. As is the case with mammalian GRK2 and GRK3, Drosophila GPRK1 includes a C-terminal pleckstrin homology domain, which binds to phosphoinositides and the Gbetagamma subunit. To address the role of GPRK1, we generated transgenic flies that expressed higher and lower levels of RK activity. Those flies with depressed levels of RK activity displayed a light response with a much larger amplitude than WT. Conversely, the amplitude of the light response was greatly suppressed in transgenic flies expressing abnormally high levels of RK activity. These data point to an evolutionarily conserved role for GPRK1 in modulating the amplitude of the visual response.
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Affiliation(s)
- Seung-Jae Lee
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Makino CL, Wen XH, Lem J. Piecing together the timetable for visual transduction with transgenic animals. Curr Opin Neurobiol 2003; 13:404-12. [PMID: 12965286 DOI: 10.1016/s0959-4388(03)00091-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Transgenic mice bearing null or functional mutations are being used to define the roles of specific elements in phototransduction and also to time the molecular interactions. Genetic manipulation of the collision frequency between rhodopsin and transducin molecules identified this parameter as rate-limiting for the photoresponse onset. Genetic interference with rhodopsin phosphorylation and arrestin binding, transducin shut-off and calcium feedback has revealed their respective roles in shaping the response waveform. The timetable for all of these molecular events determines the amplitude, kinetics and reproducibility of the photoresponse.
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Affiliation(s)
- Clint L Makino
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, 243 Charles Street, Boston, MA 02114, USA.
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Klee CB, Means AR. Keeping up with calcium: conference on calcium-binding proteins and calcium function in health and disease. EMBO Rep 2002; 3:823-7. [PMID: 12223462 PMCID: PMC1084235 DOI: 10.1093/embo-reports/kvf182] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Claude B Klee
- Laboratory of Biochemistry, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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Kutuzov MA, Solov'eva OV, Andreeva AV, Bennett N. Protein Ser/Thr phosphatases PPEF interact with calmodulin. Biochem Biophys Res Commun 2002; 293:1047-52. [PMID: 12051765 DOI: 10.1016/s0006-291x(02)00338-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Regulation of protein dephosphorylation by cytoplasmic Ca(2+) levels and calmodulin (CaM) is well established and considered to be mediated solely by calcineurin. Yet, recent identification of protein phosphatases with EF-hand domains (PPEF/rdgC) point to the existence of another group of Ca(2+)-dependent protein phosphatases. We have recently hypothesised that PPEF/rdgC phosphatases might possess CaM-binding sites of the IQ-type in their N-terminal domains. We now employed yeast two-hybrid system and surface plasmon resonance (SPR) to test this hypothesis. We found that entire human PPEF2 interacts with CaM in the in vivo tests and that its N-terminal domain binds to CaM in a Ca(2+)-dependent manner with nanomolar affinity in vitro. The fragments corresponding to the second exons of PPEF1 and PPEF2, containing the IQ motifs, are sufficient for specific Ca(2+)-dependent interaction with CaM both in vivo and in vitro. These findings demonstrate the existence of mammalian CaM-binding protein Ser/Thr phosphatases distinct from calcineurin and suggest that the activity of PPEF phosphatases may be controlled by Ca(2+) in a dual way: via C-terminal Ca(2+)-binding domain and via interaction of the N-terminal domain with CaM.
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Affiliation(s)
- Mikhail A Kutuzov
- Laboratoire de Biophysique Moléculaire et Cellulaire URA CNRS No. 520, Département de Biologie Moléculaire et Structurale, CEA-Grenoble, 38054 Grenoble cedex 9, France.
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